In adverse weather conditions, safe launch of a lifeboat from a stationary structure or a ship, which may or may not be making way, requires an expertise which few mariners possess. Launch exercises are seldom able to simulate realistic conditions as few masters are prepared to risk lives and lifeboats etc. in heavy weather conditions in order to facilitate the acquisition of skills required in the event of an emergency only.
Accidents during mandatory lifeboat drills are an ongoing issue in discussions relating to safety of seafarers.
Lifeboats are, under exercises as well as under emergencies necessitating that the crew abandon the structure or ship, either controllably lowered into the sea while carrying crew, or released, and thereby freefalling, into the sea, also while carrying crew.
Today, most lifeboat accidents are associated with on-load release functions incl. malfunctions of lifeboat hooks. On-load release involves releasing the lifeboat from its falls while the lifeboat is at least partially suspended by the falls.
The ability to on-load release a lifeboat is mandatory under IMO regulations for all ships built after Jun. 1, 1986. Ships built before this date is generally provided only with off-load release hooks, which cannot be released from its falls unless the lifeboat is fully supported by the sea.
The number of accidents and the number of people killed or injured during test or trial launches as well as launches under emergencies of lifeboats runs into the hundreds, however, there are no official records available disclosing the total number fatalities or injuries. Ship owners, operators, P&I Clubs, class societies and various other international organizations etc. are now, as a consequence, focussing on reducing the number of accidents.
In order to comply with present IMO requirements, hooks suspending lifeboats are required to have off-load release capability as well as on-load release capability.
Accidents with on-load release hooks are found to occur due to lack of maintenance, lack of knowledge in operating the hooks as well poor design, and further, it has, for various reasons, proved difficult to design and setup sufficient measures against the effects of poor maintenance and human error.
Another cause of accidents is difficulties in ensuring that, when the lifeboat is provided with two or more falls, the falls are released simultaneously from the hooks. Simultaneous release may require local release of the falls by two or more crewmembers working at opposite ends of the boat. Experience has shown that, all too often, the boat's crew has managed to release one hook only, leaving the boat suspended from the other still connected fall. In the next wave trough, the boat is upended, tipping its occupants into the water or around in the cabin of the lifeboat, with potentially serious consequences. Recognition of this problem by lifeboat manufacturers and maritime authorities, together with the introduction of partially and totally enclosed lifeboats, has led to the development of more sophisticated lifeboat release systems being able to release both falls simultaneously from a single control position, however the systems are still based on conventional hook system, wherein the at least one hook is rigidly mounted to an upwardly facing portion of the lifeboat.
Today's lifeboats of the type which are to be lowered to the surface of the sea are typically provided with one hook forward and one hook aft. The hooks are operated by release means adapted to release both hooks simultaneously as soon as the lifeboat is waterborne.
A typical embodiment consists of, as already mentioned above, two releasing hooks, one hook arranged in each end of the lifeboat and interconnected by a chain or rod running from a hook arranged at one end of the lifeboat to a hook arranged at the opposite end of the lifeboat. The chain or rod arranged between the two hooks is equipped with an operating grip arranged in a convenient location. The chain or rod is fastened to the releasing hooks in such a manner that pulling a chain or similar will cause the hooks to upset and thus free themselves from the falls. Releasing hooks interconnected by a rod, possibly arranged along the floor of the lifeboat, are operated by means of a lever acting through universal joints or similar.
Different release systems necessitate special training of the crew operating the lifeboats in order to ensure that the operators are familiar with the hook release system installed in the lifeboat at the particular vessel or rig.
Further, P&I Clubs, class societies and various other international organizations recommend that old hook systems, which are not capable of on-load release, are replaced with new hooks of improved design.
Most of the prior art hook designs are intentionally inherently unstable as the weight of the boat suspended from the hooks results in a hook opening effect, which has to be withstand by dedicated arrangements in the hooks operating mechanism.